The problem happens with the Children. The first time I assigned children and saved the User, there is no problem; but when I saved the User again (without any change on him) the values in the UserReference? table changes: the "parent_id" takes the value of the "child_id".

I test it with Sf 1.4 and with Sf 1.3 stable versions, and I've got the same error.

If it not clear to understand what I'm saying, I put a "very ilustrative" image about the form and how change the values of the UserReference? table. Please see it, because it would be very usefull for understanding (explains better than my terrible English)

Thanks for all your work!

P. D.

I forgot to to say that watching the stack trace I think that the problem is in: